Section 07-05: Transmission, Automatic—External Controls
1994 Mustang Workshop Manual
DIAGNOSIS AND TESTING

Pinpoint Tests

  

PINPOINT TEST A: SHIFT INTERLOCK SYSTEM DOES NOT RELEASE OR LOCK PROPERLY

 

A1 CHECK POWER SUPPLY TO SHIFT LOCK ACTUATOR

Yes
GO to A3.

No
GO to A2.

 

A2 CHECK FUSE 1 (15A) SUPPLY

Yes
GO to A3.

No
SERVICE Circuit 687 (GY/Y) for open circuit. RESTORE vehicle. RETEST system.

 

A3 CHECK POWER SUPPLY AT SHIFT LOCK ACTUATOR

  • Gain access to shift lock actuator as outlined.
  • Using test lamp, check power supply at shift lock actuator connector Circuit 298 (P/O).
  • Did test lamp illuminate?
Yes
GO to A4.

No
SERVICE Circuit 298 (P/O) for open circuit. RESTORE vehicle. RETEST system.

 

A4 CHECK BRAKE SWITCH POWER TO SHIFT LOCK ACTUATOR

  • Press brake pedal and hold.
  • Using test lamp, check for voltage at Circuit 810 (R/LG) at shift lock actuator connector.
  • Did test lamp illuminate?
Yes
GO to A9.

No
GO to A5. LEAVE brake pedal pressed.

 

A5 CHECK POWER AT BRAKE SWITCH

  • Using test lamp, check Circuit 810 (R/LG) for voltage.
  • Did test lamp illuminate?
Yes
SERVICE Circuit 810 (R/LG) for open circuit. RESTORE vehicle. RETEST system.

No
GO to A6.

 

A6 CHECK FOR SUPPLY TO BRAKE SWITCH

  • Using test lamp, check for voltage at Circuit 10 (LG/R) at brake switch.
  • Did test lamp illuminate?
Yes
REPLACE damaged brake lamp switch. RESTORE vehicle. RETEST system.

No
GO to A7.

 

A7 CHECK FUSE 9 (15A) OUTPUT

  • Using test lamp, check output side of fuse 9 Circuit 10 (LG/R) for voltage.
  • Did test lamp illuminate?
Yes
SERVICE Circuit 10 (LG/R) for open circuit. RESTORE vehicle. RETEST system.

No
GO to A8.

 

A8 CHECK CIRCUIT 10 (LG/R)

  • Remove fuse 9 (15A).
  • Using an ohmmeter connected to a known good ground, connect second lead to Circuit 10 (LG/R) at fuse 9. Measure resistance.
  • Is resistance 5 ohms or less?
Yes
SERVICE Circuit 10 (LG/R) or Circuit 383 (R/W) for a short to ground. RESTORE vehicle. RETEST system.

No
REPLACE damaged fuse 9 (15A). RESTORE vehicle. RETEST system.

 

A9 CHECK CIRCUIT 57 (BK)

  • Using an ohmmeter connected to a known good ground, connect second lead to Circuit 56 (BK). Measure resistance.
  • Is resistance 5 ohms or less?
Yes
REPLACE damaged shift lock actuator . RESTORE vehicle. RETEST system.

No
SERVICE Circuit 57 (BK) for open circuit. RESTORE vehicle. RETEST system.

  

PINPOINT TEST B:SHIFT CONTROL LINKAGE BINDING, OUT OF PROPER GEAR RELATIONSHIP

 

B1 CHECK SHIFT CONTROL LINKAGE

  • Gain access to shift control linkage as outlined.
  • Actuate shift linkage in all ranges.
  • Observe all linkage during operation.
  • Is linkage damaged?
Yes
REPLACE shift control linkage. RESTORE vehicle. RETEST system.

No
GO to B2.

 

B2 CHECK SHIFT CONTROL CABLE

  • Check transmission shift cable and bracket installation and tightness.
  • Is transmission shift cable and bracket properly installed?
Yes
ADJUST linkage as outlined in Adjustments. GO to B3.

No
SERVICE as necessary. RESTORE vehicle. RETEST system.

 

B3 CHECK LINKAGE/CABLE FOR PROPER GEAR RELATIONSHIP

  • Actuate shifter in all ranges.
  • Does indicator match gear selection?
Yes
SERVICE is complete. RESTORE vehicle. RETEST system.

No
REPLACE damaged linkage/cable. RESTORE vehicle. RETEST system.

  

PINPOINT TEST C:TRANSMISSION CONTROL SWITCH AND INDICATOR LAMP NOT OPERATING PROPERLY

 

C1 CHECK SUPPLY TO TRANSMISSION CONTROL SWITCH

  • Turn ignition switch to the RUN position.
  • Using a test lamp connected to a known good ground, check for voltage at output side of fuse 1 (15A) Circuit 298 (P/O).
  • Did test lamp illuminate?
Yes
GO to C3.

No
GO to C2.

 

C2 CHECK FUSE 1 (15A)

  • Remove fuse 1 (15A).
  • Using an ohmmeter connected to a known good ground, connect second lead to output side of fuse 1 (15A) cavity.
  • Measure resistance.
  • Is resistance 5 ohms or less?
Yes
SERVICE Circuit 298 (P/O) for short to ground. REPLACE fuse 1 (15A). RESTORE vehicle. RETEST system.

No
REPLACE damaged fuse 1 (15A). RESTORE vehicle. RETEST system.

 

C3 CHECK SUPPLY VOLTAGE AT CONTROL SWITCH

  • Using a test lamp, check Circuit 298 (P/O) at transmission control switch for voltage.
  • Did test lamp illuminate?
Yes
GO to C4.

No
SERVICE Circuit 298 (P/O) for open circuit. RESTORE vehicle. RETEST system.

 

C4 CHECK TRANSMISSION CONTROL SWITCH

  • Actuate the transmission control switch.
  • Using a test lamp, check for voltage at Circuit 224 (T/W) at control switch.
  • Did test lamp illuminate?
Yes
GO to C5.

No
REPLACE damaged transmission control switch. RESTORE vehicle. RETEST system.

 

C5 CHECK TRANSMISSION CONTROL SWITCH INPUT TO POWERTRAIN CONTROL MODULE (PCM)

  • Gain access to the powertrain control module as outlined.
  • Using a test lamp check for voltage at Circuit 224 (T/W) at PCM connector.
  • Did test lamp illuminate?
Yes
GO to C6.

No
SERVICE Circuit 224 (T/W) for open circuit. RESTORE vehicle. RETEST system.

 

C6 CHECK POWERTRAIN CONTROL MODULE OUTPUT TO TRANSMISSION CONTROL INDICATOR LAMP

  • Using an ohmmeter connected to a known good ground, carefully back-probe Circuit 911 (W/LG) at PCM connector.
  • Measure resistance.
  • Is resistance 5 ohms or less?
Yes
GO to C7.

No
REPLACE damaged powertrain control module . RESTORE vehicle. RETEST system.

 

C7 CHECK CIRCUIT 911 (W/LG)

  • Turn ignition switch to the OFF position.
  • Disconnect the powertrain control module .
  • Turn ignition switch to the RUN position.
  • Using a jumper wire connected to a known good ground, carefully connect other end to Circuit 911 (W/LG).
  • Did transmission control indicator lamp illuminate?
Yes
INSPECT connector. SERVICE as necessary. RESTORE vehicle. RETEST system.

No
LEAVE jumper wire connected. GO to C8.

 

C8 CHECK CIRCUIT 911 (W/LG) AT INSTRUMENT CLUSTER

  • Gain access to instrument cluster connectors as outlined in Section 13-00.
  • Using an ohmmeter connected to a known good ground, connect second lead to Circuit 911 (W/LG) at cluster connector Pin 8.
  • Measure resistance.
  • Is resistance 5 ohms or less?
Yes
GO to C9.

No
SERVICE Circuit 911 (W/LG) for open circuit. RESTORE vehicle. RETEST system.

 

C9 CHECK TRANSMISSION CONTROL INDICATOR BULB

  • Remove miniature bulb .
  • Using an ohmmeter, check continuity of miniature bulb .
  • Is there continuity?
Yes
SERVICE instrument cluster as outlined in Section 13-00.

No
REPLACE damaged miniature bulb . RESTORE vehicle. RETEST system.